Recently, in an enclosed reciprocating engine for a sterling engine, a seal portion to seal a cylinder having a piston fitted therein against a guide rod for transmitting the reciprocating motion of the piston to the outside of the cylinder is provided and sometimes uses oil. Thus, the oil leaking from the seal portion produces oil mist to pollute the interior of the cylinder, and a problem was presented that it interferes with the reciprocating motion of the piston. Hence, the oil mist in the cylinder needs to be measured during the reciprocating motion of the piston.
In conventional measuring apparatus, for example, a piezo-balance dust meter, a piezoelectric element was used for an oil mist measuring sensor. Thus it cannot be disposed in the cylinder having pressure fluctuates so as to measure directly the oil mist. That is, it samples gas in the cylinder to measure indirectly oil mist in a space separate from the cylinder after pressure is rendered constant. Thus, since accuracy in measurement was not obtained and further a sampling piping was needed, the measuring apparatus inevitably the defect of being large-scaled.
Hereinafter will be described an embodiment according to the prior art with reference to the drawings.
FIG. 5 shows a sterling engine 10 for converting energy of high temperature and pressure gas into a turning force.
Cylinders 11 including ones not shown are provided symmetrically at four positions. A piston 12 disposed in each cylinder 11 is formed on both ends with an expansion chamber 13 and a compression chamber 14. Each expansion chamber 13 and compression chamber 14 communicate respectively to heat exchangers 15a, 15b of supply sources of working gas.
In each piston 12 is disposed a guide rod 16 which transmits the reciprocating motion of the piston 12 to the outside of the cylinder 11 through a rod seal 17 system. To the guide rod 16 is connected a guide piston 18 which is slidably disposed in a guide cylinder 19. Each guide piston 18 engages a swash plate 20 which has a rotary shaft 21.
The engine 10 thus constituted is supplied with high temperature and pressure helium gas sequentially through the heat exchangers 15a, 15b and each piston 12 reciprocates cyclically in the cylinder 11.
This reciprocating motion is transmitted through the guide rod 16 and the respective guide pistons 18 reciprocate with a certain phase difference therebetween. Thus, the swash plate 20 engaging each guide piston 18 will rotate and the rotation is transmitted to the outside through the rotary shaft 21.
Here, will be described the constitution of the rod seal system 17 for maintaining the cylinder 11 air-tight against the guide rod 16 with respect to FIG. 5.
The rod seal system 17 is constituted such that around the guide rod 16 from the compressor chamber 14 side are sequentially disposed a gas seal 26, an intermediate chamber 25 communicating to the compression chamber 14, an oil scraper 22, a liquid enclosing chamber 23 and an oil seal 24, and the liquid enclosing chamber 23 communicates to the upper portion of the oil scraper 22 through an oil tank 27.
Thus, since oil is used for sealing, oil disposed in the liquid enclosing chamber 23 has a possibility of leaking to the compression chamber 14 through the oil scraper 22, intermediate chamber 25 and gas seal 26. Hence, in the compression chamber 14 of the engine 10 will be distributed oil in the form of mist.
This oil mist deposits on the inside wall of a pipe of the heat exchanger through a pipe interconnecting the heat exchanger and the compression chamber 14.
As the deposit of this oil mist on the inside wall of the pipe is accumulated, gas flow path in the pipe will be blocked to degrade the efficiency of heat exchange of helium gas while degrading the efficiency of engine itself.
Also, when the efficiency of the filter 28 is degraded, the oil mist will be similarly in the form of mist distributed in the compression chamber 14 through the oil scraper 22, intermediate chamber 25 and filter 28.
Thus, the detection of oil mist concentration in the compression chamber 14 of the engine 10 is an important subject for maintaining the performance of the compressor.